Explain how Paul was changing and growing up

Paul's maturing from a teenage boy to a grown man is a central theme in the novel. His maturity comes in many different forms. He matures physically, growing taller than most of his classmates between his first and second year. Paul also experiences sexual maturity. He develops in sensuality, has his first sexual experiences, and learns to distinguish between his childhood lust for Megan and his deep, emotional love for Rosie. He also develops in his understanding of Keller's life and, consequentially, his understanding of the world. He goes from making immature jokes about Keller being a war criminal in hiding, to having a deep respect for his professor and what he has endured. Through knowing Keller, Paul comes to learn more about the cruelties of the world. He also matures in his perspective on his relationship with Keller, realizing more and more the impact Keller has had on his life.